1. Field of the Invention
Example embodiments of the present invention relate generally to thin-film transistor (“TFT”) arrays. More particularly, example embodiments of the present invention relate to a TFT with decreased variation in threshold voltage and improved electrical reliability, an array substrate having the TFT, and a method of manufacturing the TFT.
2. Description of the Related Art
Generally, flat panel display devices include an array substrate with a number of switching elements and a counter substrate opposite to the array substrate. Each switching element includes a gate electrode connected to a gate line, a semiconductor pattern electrically insulated from the gate electrode, a source electrode connected to a data line to be electrically connected to the semiconductor pattern, and a drain electrode spaced apart from the source electrode to be electrically connected to the semiconductor pattern.
The switching elements may be, for example, amorphous-silicon (a-Si) TFTs, poly-silicon (poly-Si) TFTs, oxide semiconductor TFTs, etc.
The a-Si TFT has is the benefit of being readily formed in uniform manner on large size substrates and are thus relatively low cost. However, the a-Si TFT has relatively low charge mobility. In contrast, poly-Si TFTs have the benefit of high charge mobility, so that deterioration of the switching element's characteristics is small in comparison with the a-Si TFT. However, the poly-Si TFT liquid crystal display (LCD) has a more complex manufacturing process than the a-Si TFT, so that its manufacturing cost is higher than that of the a-Si TFT.
The oxide semiconductor TFT may be manufactured in a low temperature process, and may be utilized in large size display panels. In addition, the oxide semiconductor TFT may have high charge mobility. However, the oxide semiconductor TFT requires a bias voltage to be applied to one electrode, resulting in threshold voltage that can vary with time. This reduces the electrical stability and reliability of the switching element.